1. Field of the Invention
The present invention pertains to multi-speed hydraulically actuated powershift type gear transmission having four speeds in forward and reverse and an improved arrangement of directional clutches and hydraulic control valves.
2. Background
In the art of multi-speed powershift type gear transmissions there are several problems which confront the art worker in any effort to design a transmission having a particular number of speed ranges of the output shaft relative to the input shaft in both forward and reverse direction. In certain vehicle applications it is highly desirable to provide a transmission having as many as four output shaft speeds in both forward and reverse direction of shaft rotation. In order to provide a cost effective, easily manufacturable and easily serviceable transmission the art worker is then confronted with the problem of selection of the number of and arrangement of the directional and speed range clutches as well as the number of gears required to achieve the requisite speed ranges in both forward and reverse.
Another problem in the art of powershift transmissions pertains to the accessibility of the directional clutches, in particular. In many applications of powershift transmissions the directional clutches are subject to particularly heavy use and rapid wear and are desirably easily accessible for servicing and repair without disassembly of the transmission itself.
Still further problems associated with powershift transmission design pertain to the location of the hydraulic control valving for the directional and speed range clutches in order to minimize flow losses and improve clutch engagement and disengagement response time.
The abovementioned desiderata and problems related to the art of powershift gear transmissions have been satisfied and overcome, respectively, by a multi-speed powershift transmission in accordance with the present invention.